DROSOPHILA SYNTAXIN IS REQUIRED FOR CELL VIABILITY AND MAY FUNCTION IN MEMBRANE FORMATION AND STABILIZATION

The role of the Drosophila homologue of syntaxin-1A (syx) in neurotran smission has been extensively studied. However, developmental Northern analyses and in situ hybridization experiments show that SYX mRNA is expressed during all stages and in many tissues. We have isolated new mutations in syx that reveal roles for syx outside the nervous system. In the ovary, SYX is present in the germarium, but it is predominantl y localized to nurse cell membranes. Mitotic recombination experiments in the germline show SYX is essential for oogenesis and may participa te in membrane biogenesis in the nurse cells. In the early embryo, a l arge contribution of maternally deposited RNA is present, and the prot ein is localized at cell membranes during cellularization. After the m aternal contribution is depleted, zygotically produced SYX assists sec retion events occurring late in embryogenesis, such as cuticle deposit ion and neurotransmitter release. However, SYX is also required in lar val imaginal discs, as certain hypomorphic mutant combinations exhibit rough eyes and wing notch defects indicative of cell death. Furthermo re, recombinant clones that lack syx cause cell lethality in the devel oping eye. We propose that, similar to its roles in cuticle secretion and neurotransmitter release, SYX may mediate membrane assembly events throughout Drosophila development.